During a SharePoint 2010 training class i was conducting this week we were implementing a case originally created for MOSS 2007, where the author of the case had added a requirement to show a PowerPoint deck in a SharePoint page. This threw me a bit off, as I couldn't remember seeing any direct functionality for this. I turned out that the author had intended the students to research 3rd party solutions for this.
I started thinking about Office Web Apps. "Where are the built in Office Web Apps webparts" I thought.. Nowhere, it would turn out, so I started to experiment with a good old friend; the PageViewer webpart.
Using the Office Web Apps link to a SharePoint 2010 hosted document directly will not work, because its blocked for use in frames (PageViewer is just an iframe you know..). But if you open a document in Office Web Apps, and then click the Pop-Out button you'll get another URL which does.
This could be a starting point for a nice little codeplex webpart solution some time in the future. Until then; enjoy the PageViewer:-D